Oxygen-18 isotope effect in carbon-13 nuclear magnetic resonance spectroscopy. 2. The effect of structure

Risley, John M.; Etten, Robert L. Van

doi:10.1021/ja00534a007

Cited by 90 publications

(60 citation statements)

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“…The data (Table IV) qualitatively confirm earlier measurements performed at a lower magnetic field (12). However, the magnitude of measured upfield shifts (ϳ4.5 Hz; (19) for bond orders of 1.5 (carboxyl oxygen; 0.025 ppm) and 2 (carbonyl oxygen; 0.05 ppm), the current results are closer to the value for a carboxyl oxygen. Due to the sulfur atom in the thioester linkage, the thioesterified carbonyl carbon has more ketone character than expected for the comparable carbon in oxoesters or carboxylic acids; this accounts for the 204-ppm signal for [1-13 C]acetyl-CoA in solution.…”

Section: Discussionsupporting

confidence: 89%

The Influence of Conserved Aromatic Residues in 3-Hydroxy-3-methylglutaryl-CoA Synthase

Misra

Wang

Miziorko

2003

Journal of Biological Chemistry

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In order to evaluate the potential contribution of conserved aromatic residues to the hydrophobic active site of 3-hydroxy-3-methylglutaryl-CoA synthase, site-directed mutagenesis was employed to produce Y130L, Y163L, F204L, Y225L, Y346L, and Y376L proteins. Each mutant protein was expressed at levels comparable with wild-type enzyme and was isolated in highly purified form. Initial kinetic characterization indicated that

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Section: Discussionsupporting

confidence: 89%

The Influence of Conserved Aromatic Residues in 3-Hydroxy-3-methylglutaryl-CoA Synthase

Misra

Wang

Miziorko

2003

Journal of Biological Chemistry

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“…This was acidified under nonaqueous conditions and trapped by diazomethane esterification as its methyl ester 18 to avoid possible exchange of oxygen at the carboxyl. Examination of the 13c nmr spectra of 18 shows ''0 isotope shifts of the expected magnitude (32,33) at the carbonyl carbon (A6 = 0.015 and 0.038 ppm) and at the methyl carbon (A6 = 0.026 ppm) but no detectable shift at the hydroxyl carbon, C-3. The complete lack of oxygen-18 at the hydroxyl was confirmed by comparison of the mass spectra of 18 and the isotopic isomer ).…”

Section: Resultsmentioning

confidence: 96%

“…In order to determine the isotopic content, a portion was treated with a-bromo-p-phenylacetophenone using the method reported for preparation of p-bromophenacylformate (33 The p-lactone 2 (59.6 mg, 0.27 rnmol) was added to a solution of potassium ['802]acetate (142 mg, 1.39 rnmol) in dimethylformamide (6 mL) and water (0.5 mL). Themixture was stirred 1.5 h, water (6 mL) was added, and the solution was acidified to pH 2 with 1 N HCl.…”

Section: Potassium [1802]acetatementioning

confidence: 99%

Mechanism of formation of serine β-lactones by Mitsunobu cyclization: synthesis and use of L-serine stereospecifically labelled with deuterium at C-3

Ramer¹,

Moore²,

Vederas³

1986

Can. J. Chem.

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. VEDERAS. Can. J. Chem. 64, 706 (1986).The ring closure of N-benzyloxycarbonyl-L-serine (1) under Mitsunobu conditions (Ph3P, dimethyl azodicarboxylate, -78°C) to give the corresponding p;lactone (2) is shown by deuterium and oxygen-18 labelling studies to proceed by hydroxy group activation, in contrast to analogous cyclizations of more hindered P-hydroxy acids, which usually occur by carboxy group activation. Samples of 1 stereospecifically labelled with deuterium at C-3 were prepared by hydrogenation of (2)-2-acetamido-3-methoxyacrylic acid (9) with deuterium, followed by selective Acylase I deacetylation of the 2 s isomer, removal of the protecting groups, and N-acylation of the resulting L-serine with benzyl chloroformate. Mitsunobu cyclizations of this 3R deuterated N-acyl serine, of the [hydroxy-'80] analog l g , and of the [ c a r b~x~- '~O ] derivative If show that lactonization occurs with inversion of configuration at C-3, loss of the hydroxy oxygen, and retention of the carboxy oxygens. Similar labelling experiments demonstrate that aqueous sodium hydroxide opens the p-lactone ring by exclusive attack at the carbonyl to regenerate 1 , whereas acidic hydrolysis proceeds primarily by attack of water at the C-3 methylene group of 2. This information allows interconversion of L-serines that are stereospecifically labelled at C-3 with hydrogen isotopes and affords access to other labelled P-substituted alanines. SHAWN E. RAMER, RICHARD N. MOORE et JOHN C. VEDERAS. Can. J. Chem. 64,706 (1986).Faisant appel a des etudes par marquage au deuterium et a l'oxygkne-18, on a dCmontrC que la cyclisation de la N-benzyloxycarbonyl L-strine (I), dans des conditions de Mitsunobu (Ph3P, azodicarboxylate de dimethyle, -7g°C), qui conduit h la formation de la p-lactone corespondante se produit par le biais d'une activation du groupement hydroxyle; ceci est en opposition avec ce qui se produit lors de cyclisations analogues d'acides P-hydroxyles plus empCchCs qui se produisent habituellement par le biais d'une activation du groupement carboxyle. On a prtpart des tchantillons de 1 marques sttr6os@cifiquement par du deuterium en C-3 en proctdant a une hydrogenation de l'acide acktamido-2 methyoxy-3 acryliques-(2) (9) avec du deuterium suivie d'une deacetylation stlective de l'isomkre 2-(S) par 1'Acylase I, de l'enlkvement des groupes protecteurs et finalement d'une N-acylation de la L-strine qui en rCsulte par du chloroformate de benzyle. Les cyclisations, selon Mitsunobu, de cette N-acyl sCrine deutkrte en 3(R), de son analogue l g portant un hydroxyle "0 et du derive lf portant un carboxyle ''0 demontrent que la lactonisation se produit avec une inversion de configuration en C-3, avec une perte d'oxygkne de l'hydroxyle et avec retention des oxygknes des groupements carboxyles. Des experiences semblables de marquage ont permis de dkmontrer que, sous l'influence de l'hydroxyde de sodium aqueux, le cycle de la p-lactone s'ouvre par une attaque qui se produit exclusivement au niveau du groupement carbonyle pour regentrer l...

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“…The highfield isotopic shift of the carbonyl carbon atom ( 13 C NMR) was exactly 50 ppb, as expected. 16 A MS of the ketone indicated the practically complete incorporation of the label. Similarly, compound 1b gave 2b * (Dd = 0.050 ppm).…”

Section: 14bmentioning

confidence: 99%

Catalytic, PMe3-mediated conversion of secondary nitroalkanes to ketones: a very mild Nef-type process

Burés

Vilarrasa

2008

Tetrahedron Letters

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Aliphatic secondary nitro compounds are converted to ketones at room temperature, usually in 90-100% yields, by a one-pot reaction with 220-250 mol % of trimethylphosphine (PMe 3 ) and 50-100 mol % of and, in the case of primary nitro groups, into nitrile oxides (for 3 + 2 cycloadditions) 5 and nitriles. 3b,6 Many methods, most of them oxidative, are also known for the conversion of nitro to carbonyl compounds (Nef-like reactions), 7 connecting the organic chemistry of the nitrogen compounds with the carbonyl chemistry. We report here a reductive method for the quick conversion of secondary nitroalkanes to ketones that can be performed at room temperature (rt).The new method relies upon the use of the most reactive trialkylphosphine (namely PMe 3 ) 8 as the reducing agent and a suitable catalyst, and was inspired by a report of Zard et al., 9 who treated c-nitroketones and nitro-steroids with excesses of tributylphosphine (PBu 3 ) and diphenyl disulfide (PhSSPh) to obtain pyrroles and oxo-steroids, respectively. As in any reductive method, 7 nitro derivatives or their nitronate ions are expected to give the intermediate oximes (the main tautomers of the nitroso compounds) or their anions, which may be then converted to the imines in situ (Scheme 1); during the workup, the imines may be hydrolyzed to ketones (or reduced to amines or transformed to other functional groups).7,9a,b After an exhaustive search for reagents and catalysts that could work in an acceptable time and turnover at rt, we have found that PMe 3 and 4,4 0 -bis-tert-butyldiphenyl disulfide 0040-4039/$ -see front matter Ó

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Oxygen-18 isotope effect in carbon-13 nuclear magnetic resonance spectroscopy. 2. The effect of structure

Cited by 90 publications

References 1 publication

The Influence of Conserved Aromatic Residues in 3-Hydroxy-3-methylglutaryl-CoA Synthase

The Influence of Conserved Aromatic Residues in 3-Hydroxy-3-methylglutaryl-CoA Synthase

Mechanism of formation of serine β-lactones by Mitsunobu cyclization: synthesis and use of L-serine stereospecifically labelled with deuterium at C-3

Catalytic, PMe3-mediated conversion of secondary nitroalkanes to ketones: a very mild Nef-type process

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